Process of making fiber for paper, etc



VIGGO DREWSlEN, F BROOKLYN, NEW YORK, ASSIGNOR TO WEST VIRGINIA PULlPNEW YORK, N. Y., A CORPORATION OF DELAWARE.

AND rarer. COMPANY, or

PROCESS OF MAKING FIBER FOR PAPER, ETC.

No Drawing. Application filed July 19, 1920, Serial N 0. 397,484.Renewed November 14, 1922. serial No. 600,987. a

Be-it known that I, VIGGO DREWSEN, a

, citizen of the United States, and resident of the borough of Brooklyn,county of Kings, city and State of New York, have made certain new anduseful Improvements Relating to Processes of Making Fiber for Paper,Etc, of which the following is a specification.

Thisv invention relates especially to processes for producing fiber fromwheat straw, rice straw, etc., by treating the raw fibrous materialunder pressure in a suitable monosulphite solution and then, preferably,after removing the treating liquor, subjecting the fiber to a secondacid treatment as in a bisulphite solution to further purify the fiberand facilitate bleaching.

With wheat straw, rice straw, and other suitable cereal straws such asbarley, rye, oat and flax straw, the raw fibrous material may be cookedfor four to eight hours or so in a monosulphite solution. under apressure of sixty to ninety pounds more or less, to remove from thecellulose at least the larger part of the soluble material which givesthe cooking liquor a dark greenish or brownish tinge. This waste liquorcan advantageously be converted by treatment with slaked lime whichcombines with the organicv material thus releasing and precipitating themagnesium compounds it the "sulphite used is the normal or monosulphiteof magnesium. It is still better to use dolomite lime for this treatmentof the waste liquor; since,

in this case, the lime combines with the organic compounds precipitatingthe magnesium compounds from the dolomite together with thosedisplacedfrom the waste liquor.

The fibrous material, after this first or preliminary treatment withmagnesium, so dium or other soluble sulphite, preferably of alkalinecharacter and reaction, can advantageously be treated with a' suitableacid treating liquor such as sulphuric or sulphurous acid or the acidsulphites or sulphates, these being cheap and available acid materials.A desirable way of effecting this acid treatment is to have the fiberpulp suspend; ed in enough water so as to pump freely and then run thesame through a treating, scrubbing or percolating tower into whichsulphur dioxide may be run, preferably in hot condition from the sulphurburners, etc. after a preliminary electrostatic purification.

This treatment, which may be efiected at atmospheric or moderatepressure in some cases, should be continued until the acid hasthoroughly acted on the plup liquor and gives it an acid reaction; theacid treatment dissolves out some further organic material which givesthe li nor a dirty greenish tinge and leaves the pn p in a very muchcleaner and whiter condition so that the subsequent bleaching of thepulp is greatly simplified, only a few per cent of bleach being requiredto give thoroughly satisfactory results, and for some purposes furtherbleaching is unnecessary, which makes possible a still higher yield ofstrong fiber. After this sulphur dioxide treatment the liquor may be runthrough a screen to remove the pulp and the liquor reused for anothertreatment in some cases, which prevents waste of the absorbed sulphurdioxide, the absorbed gas being, of course, recovered by beingeliminated by heat treatment of the final liquor when its reuse isundesirable. This sulphur dioxide or other acid treatment of the pulpproduces in the treating liquor, acid sulphites of magnesium or othermaterial; so that the fibrous material is first treated with an alkalinetreating solution and then with an acid solution which more thoroughlyeliminates all soluble components without drastic or injurious action onthe fiber.

Incommercially operating this process, the first waste liquor from theraw fibrous material may be treated with calcined and slaked dolomite inpowdered form and this brings down, with the magnesia of the dolomite,the magnesia which had been held in organic solution in the wasteliquor, both vthese magnesia components being removed byfilter-pressing. This magnesia is preferably purified by calcining toeliminate any traces of combined organic material, and then it may bedissolved by carbon dioxide treatment under pressure to produce the acidmagnesium carbonate or bicarbonate of magnesium. This solution mayadvantageously be filter-pressed which thus removes any silica or otherinsoluble material;

and the solution may then be treated with magnesium acid sulphite whichproduces the normal sulphite of ma esia and liberates carbon dioxidewhic may be reused in' the other step of the process to the extentnecessary and the surplus sold.

A surplus of magnesia is also produced in this process which can bedisposed of so as to help pay for the primary raw treatpyrites.

ing materials, dolomite and sulphur or may be transformed into thebisulphite form by treatment with sulphur dioxide, for use in theforegoing step of the process.

It is sometimes desirable, also, to treat the calcined magnesia whichmay be produced as above described from the first waste liquor of theprocess with sulphur dioxide in water suspension to form magnesiummonosulphite; or, if desired,- the original magnesia precipitated fromthe waste liquor may be treated with sulphur dioxide without suchcalcining purification treatment so as to form the monosulphite orbisulphite directly therefrom. Where sodium monosulphite is usedas thetreating liquor the soda may be recovered, as by evaporating ,andcalcining or dry distilling the waste sulphur dioxide.

whilecarbondioxidejs set free.

liquor, and then leaching may be used tov recover the soda in caustic,carbonate or sulphate form. It is preferable however, to

Rice straw, when treated with magnesium monosulphite or other suitablemonosulphite in the manner described, is uite completely separated intoits ultimate bers which are extremely fine and strong; and thesedelicate fibers are not appreciably injuredor seriously reduced instrength by this'treating agent. The diameter of'these ultimate .ricestraw fibers is about .006 mm. which is,

of course, very much finer than wheat straw fiber which has a diameterof about .020 mm. while sulphite fiber has an average diameter or widthof about .030 min. This rice straw fiber, which may, of course, be

' bleached and refined in various ways,

especially by treatment with an acid sulphite solution after removal ofthe original monosulphite cooking liquor, is especlally desirable forfine or high-grade papers including Bible paper, tissue paper, cigarettepaper, etc. The small diameter of this rice straw fiber, which isractically the same length as the fiber o wheat straw, etc., gives tothe rice straw fiber extremely good felting or paper-making qualities sothat strong and tough paper can readily be produced even in extremelythin grades.

In some cases for cheaper grades of paper, card-board etc., wheat, riceor oat straw Part of the magnesium sulphite' may be under-cooked withmagnesium or sodium monosulphite, so that a large part but not all ofthe connective tissue is dis solved or removed. A treatment of two tofour hours under a pressure of forty to sixty pounds or so per squareinch, usually gives this result and renders the fibrous materialsufficiently separable, so that by a beating or mechanical refiningtreatment, the fiber may be rendered suitable for news print or othermedium grade papersand a yield of fifty to sixty per cent or more ofsuch relatively coarse fiber can be secured from some grades of ordinarywheat straw for instance.

This invention has been described in connection with a number ofillustrative materials, proportions, conditions, arrangements'and ordersof steps, to the details of which disclosure the invention is not ofcourse to be limited, since what is claimed as new and what is desiredto be secured by Letters Patent is set forth in the appended claims:

1. The process of producing fiber from cereal straw which comprisescooking the same under pressure in a strong water solution of magnesiummonosulphite, removin the treating liquor and suspending the fi r inwater to form a flowable pulp and repeatedly treating the pulp with hotsulphurous acid gas to dissolve and remove additional organic'materialand form a readily bleachable strong fiber.

2. The process of producing fiber from cereal straw which comprisescooking the same under pressure in a solution of magnesium monosulphiteand repeatedly treating the treated fiber with hot sulphurous acid gasto dissolve and remove additional organic maierial and form a readilybleachable strong ber.

3. The process of, producing paper fiber from cereal straw whichcomprises cooking the same under pressure in a strong water solutionv ofsoluble monosulphite, removing the treating liquor and suspending thefiber in water to form a fiowable pulp and treating the pulp withsulphurous acid material to dissolve and remove additional organicmaterial.

4. The process of producing paper fiber from cereal straw whichcomprises cooking the-same under pressure in a solution of S01- ublemonosulphite, removing the treating liquor and suspending the fiber inwater to form a flowable pulp and treating the pulp with an acid reagentto dissolve and remove additional organic material.

5. The process of producing fiber from cereal straw or other raw fibrousmaterial whlch comprises cooking the same. under pressure in a solutlonof. alkaline-monosulphite, and subjecting the fibrous material to anacid treatment dissolve and remove ad LMLQM ditional organic materialand form a more readily bleachable strong fiber.

6. The process of producing paper fiber from wheat straw which comprisesboiling the straw under pressure in a soluble monosulphite solutionhaving an alkaline reaction and treating the fiber with a hot acidsulphite solution to remove additional organic gnaterial and promote thebleaching of the ber.

7. The rocess of producing fiber from straw which comprises boiling thestraw under pressure in a soluble monosulphite solution and treating thefiber with a hot acid sulp-hite solution to remove additional organicmaterial and promote the bleaching of the fiber.

8. The process of producing paper fiber from wheat or rice straw whichcomprises boiling the straw under pressure in a m esium monosulphitesolution having an aline reaction, removing the treating liquor andtreating the fiber with a hot acid sulphite solution to removeadditional organic fpgeterial and promote the bleaching of the 9. Theprocess of producing paper fiber from straw which comprises boiling thestraw under pressure in a magnesium monosulphite solution having analkaline reaction and treating the fiber with a hot acid solution toremove additional organic material and promote the bleaching of thefiber.

VIGGO DREWSEN.

